In the speakers, such as in-vehicle speakers, which are employed under conditions of limited spaces for disposition, thinning the speakers is necessarily required for responding to the requirement for space reduction.
For the response thereto, there have been suggested various measures for rendering the speakers thinner in their entire dimensions with an inner-magnet type magnetic circuit disposed in a space in front of the cone-shaped diaphragm, so that any parts of the magnetic circuit will not project rearward of the speaker.
As an example of prior art references attempting the thinning of speakers, there has been, for example, a Japanese Patent No. 2,685,175. FIG. 7 shows a sectioned view of the speaker disclosed therein.
In this speaker, the thinning of the speaker is accomplished by placing a magnetic circuit 20, diaphragm 21 and so on between a basket 22 disposed on the front side and a basket 23 disposed on the rear side, the baskets thus being in a paired front-and-rear arrangement in which the magnetic circuit 20 is supported by the front basket 22 and a vibration system is supported by the rear basket 23, and by enclosing the vibration system comprising the magnetic circuit 20, diaphragm 21, and so on, between these front and rear baskets 22 and 23.
However, in this prior art, there has been a problem that, because the magnetic circuit 20 is supported by the front basket 22 and the cone-shaped diaphragm 21 is provided on the rear side thereof, the front side of the sound radiating surface of the cone-shaped diaphragm 21 is covered by the front basket 22, which gives a bad influence on the acoustic characteristics.
As examples of the prior art references which have solved this problem, there are Japanese Utility Model Registration Nos. 2,579,525 and 3,001,527. FIG. 8 shows the speaker of the former, and FIG. 9 shows the speaker of the latter.
In these speakers, there is adopted a configuration in which the magnetic circuit 30 is supported by a supporting body 31 on the rear side of the diaphragm.
Consequently, there exists no hindrance against the sound on the front side of the sound radiating surface of the diaphragm 32, resulting in preventing damaging or degrading the acoustic characteristics.
However, in any of the above-described configurations, because there is no application of an ordinary assembling method in which the inner circumferential surface of the voice coil 33 is controlled by means of a gap gauge to position and mount the voice coil 33 in the magnetic gap, there is a problem that the assembling in high precision cannot be attained and such troubles as rubbing action of the voice coil and so on is apt to occur.
Further, there is some disadvantage in the aspect of the strength because of the unitary structure of the frame.
The present invention has been suggested in order to solve the foregoing problems, and its object is to provide a thin speaker and a method of manufacturing the speaker, wherein the thin speaker having an inner-magnetic type magnetic circuit disposed on the front side of a cone-shaped diaphragm can be obtained without provoking any degradation of the acoustic characteristics, and highly-precise assembling can be realized through simpler steps without causing any rubbing of the voice coil and so on, but with sufficient strength obtained.